I
idea, imagination, conception, and ideal
idleness, recreation, repose, and rest
ignominious, infamous, despicable, and contemptible
illumine, instruct, enlighten, and inform
imaginative, sensitive, nervous, and highly-strung
impatience, indolence, wastefulness, and inconclusiveness
impel, stimulate, animate, and inspirit
imperious, wayward, empirical, and impatient [imperious = arrogantly domineering or overbearing]
improvident, incautious, prodigal, and thriftless
impudent, insolent, irrelevant, and officious
inadvertency, carelessness, negligence, and oversight
indecision, doubt, fear, and lassitude
indifference, caution, coldness, and weariness
indolent, passive, sluggish, and slothful
ineffectual, powerless, useless, and unavailing
infamy, shame, dishonor, and disgrace
infantile, childish, boyish, and dutiful
informal, natural, unconventional, and careless
insolent, impudent, impertinent, and flippant
integrity, frankness, sincerity, and truthfulness
intellectual, moral, emotional, and esthetic
intense, earnest, violent, and extreme
invent, discover, design, and contrive
inveterate, confirmed, chronic, and obstinate
invidious, envious, odious, and offensive
invincible, unconquerable, insurmountable, and insuperable
irksome, tiresome, tedious, and annoying
irregular, uncertain, devious, and unsystematic
irritable, choleric, petulant, and susceptible